1. Field of Invention
This invention relates generally to electrotherapy, and more particularly to an electrical stimulation technique and apparatus therefore for conducting a direct-current through the skin, or through tendons and ligaments or other damaged tissue in order to facilitate the regeneration thereof as well as to promote blood reperfusion in damaged tissue, such as in nerves.
2. Status of Prior Art
Electrical currents passing through a biologic system can give rise to thermal, physiochemical and physiologic effects. It is now recognized that electrical currents applied to damaged tissue may be conducive to tissue growth and repair. In applying these currents, various techniques have heretofore been used, such as surgical implantation of current-delivering electrodes.
It is well known in electrotherapy that one can promote healing of damaged tissue by subjecting the tissue to an electromagnetic field produced by inductive coupling means, or to an electrostatic field created by capacitive coupling means. In conradistinction, the present invention resides in an exogenous electrical stimulation technique in which electrodes are placed within or near the damaged tissue region to cause, when a DC potential is impressed across the electrodes, an ionic and electronic current to flow through the tissue region being treated. The magnitude of this potential is usually about 1.5 volts to avoid electrolysis and the resultant release of gas, the current flowing through the tissue region being in the milliampere or microampere range.
A detailed disclosure of various electrical stimulation techniques can be found in the article by Black entitled "Electrical Stimulation of Hard and Soft Tissue in Animal Models," which appears in Plastic Surgery, Vol. 12, No. 2, Apr. 25, 1985.
In stimulating wounded tissue with an electrical current, the healing modes are generally of two kinds, primary and secondary. In primary repair, the damaged tissues are left in their original positions or are reapproximated, and they are caused to heal by a renewal of cells at the site of injury. In secondary repair, the tissues are not reapproximated, and in many cases will exhibit a gap where a portion of the tissue has been excised. In an early cell growth and proliferation stage, this gap is bridged by a granulation bed which remodels and matures into a fibrous scar. A "wound module" is created which is a complex of tissues and cell populations that migrate into the wound from the edges of the lesion. Successive stages of coagulation, inflammation tissue elaboration and remodeling occur. Artificial intervention by electrical stimulation serves to accelerate any or all of these phases.
The cellular events which take place in the course of regenerating damaged living tissue are described in detail in the chapter entitled "The Physiology of Wound Healing" included in the text "Wound Healing and Wound Infection" by T. K. Hunt; Appleton-Century Crafts--1980.
When most tissues are traumatized, an "injury current" is produced, which is positive relative to the surrounding tissue. In biological tissues, current is carried by ions, not electrons; hence the injury current is an ionic current flowing in the direction in which positive ions (cations) move. When cells and tissues are damaged, ions "leak" from their compartmentalized and charge-separated medium to the immediate environment.
The skin, for example, acts as a membrane with an internal positive charge. In damaged skin, there is a steady injury current which is driven outward, so that there is an external positivity with respect to the adjacent uninjured areas. Although there is inadequate evidence to support the hypothesis that electrical currents flowing through the damaged tissue can alter the injury current, it is not unreasonable to assume that it does have an effect. Moreover, there may be additional cellular mechanisms only peripherally related to the injury current upon which applied electric currents exert their influence.
The regeneration of damaged body parts in a skin wound healing process commences with the growth and proliferation of cells. The tissues having the greatest capacity for repair are generally those subject to the greatest chance of traumas such as bone, cartilage, tendon, muscle, skin, blood vessels, peripheral nerves and mucose. Most methods heretofore developed to enhance the natural healing process involve some kind of pharmacological intervention, although medical devices such as sutures and staples are commonly used in surgical practice. Other methodologies are somewhere in between. An example is the use of exogenously applied electrical fields which can serve to alter the course of tissue response to injury. The electrical fileds can be applied in an alternating-current (AC) manner or in a direct-current (DC) manner, either in a steady state or in a pulsed mode.
The references listed below discuss various exogenous electrical signal techniques for stimulating the regeneration and repair of damaged tissue.
1. Bassett, C. A. L., Mitchell, S. N. and Gaston, S. R. Treatment of ununited tibial diaphyseal fractures with pulsing electromagnetic fields. J. Bone and Joint Surgery. 63A:511, 1981.
2. Brighton, C. T., Friedenberg, Z. B., Mitchell, E. I., and Booth, R. E. Treatment of nonunions with constant direct current Clin. Orthop. Relat. Research 124:106, 1977.
3. Assimacopoulos, D. Wound healing promotion by the use of negative electric current. Am. Surgeon. 34:423, 1968.
4. Bigelow, J. B., Al-Husseini, S. A., Von Recum, A. F. and Park, J. B. Effect of electrical stimulation of canine skin and percutaneous device--skin interface healing in D. T. Brighton, J. Black and S. R. Pollack (eds.), Electrical properties of Bone and Cartilage: Experimental Effects and Clinical Applications. N. Y. Grund and Stratton 1979, p. 289.
5. Konikoff, J. J. Electrical promotion of soft tissue repairs. Ann. Biomed. Engineering 4:1, 1976.
6. Brummer, S. B. and Roblee, L. S. Criteria for selecting electrodes for electrical stimulation: theoretical and prectical considerations. Ann. N. Y. Acad. Sciences 405:159, 1983.
7. Laub, F. and Korenstein, R. Actin polymerization induced by pulsed electric stimulation of bone cells in vitro. Biochem, Biophys. Acts. 803:308, 1984.
8. Korenstein, R., Somjen, D., Fischler, D. and Binderman, I. Capacitive pulsed electric stimulation of bone cells; induction of cyclic-AMP changes and DNA systhesis. Biochem. Biophys. Acta. 803:302, 1984.
9. Roden, G. A., Bourret, L. A. and Norton, L. A. DNA synthesis in cartilage cells is stimulated by oscillating electric fields. Science 199:690, 1978.
10. Roley, B. A., McKenna, J. M., Chase, G. R. and Wolcott, L. E. The influence of electrical current on an infecting microorganism in wounds. Ann. N. Y. Acad. Sciences 238:543, 1974.
11. Wolcott, L. E., Wheeler, P. C., Harwicke, H. N. and Rowley, B. A. Accelerated healing of skin ulcers by electro-therapy: preliminary clinical results S. Med. J. 62:795, 1969.